Big hole drilling bit

ABSTRACT

A big hole drilling bit of the type utilizing a plurality of roller cutters mounted for cutting in a plane perpendicular to the axis of rotation of the bit. Regrinding of cuttings is reduced by providing baffles in association with individual roller cutters to prevent the normal pumping action of the cutters from depositing their own cuttings in front of them. Baffles may merely disrupt the pumping action of the roller cutters or they may be designed to utilize the pumping action to assist in transporting cuttings toward a pickup opening through which the transport of the cuttings to the earth&#39;&#39;s surface is initiated.

United States Patent Grovenburg et al. Oct. 2, 1973 BIG HOLE DRILLINGBIT 2,654,578 10/1953 Pearce 175 313 1751 William Tulsa, $123123? #1323Elflfifijiii "lei/ 51 3; -1 Robe" Gaul, Las Vegas, 3,674,314 7/1972Scaravilli 175 313 x 3,583,503 6/l97l Cosk| 175/313 [73] Assignee: TheUnited States of America as represented by the United States PrimaryExaminer-Dav1d H. Brown Atomic Energy Commission, Attorney-Roland A.Anderson Washington, DC. [221 Filed: Mar. 6, 1972 [57] ABSTRACT A bighole drilling bit of the type utilizing a plurality of [21} PP N05232,159 roller cutters mounted for cutting in a plane perpendicular tothe axis of rotation of the bit. Regrinding of cut- 52 U.S. c1 175/313,175/353, 175/376 tings is reduced by Pmviding baffles association with.51 Int. Cl E2lb 9/12 individual Prevent the normal Pumping 581 Field ofSearch 299/90; 175/313, action Cutters from depositing their OwnCuttings 175531, 336 350, 353 376 in front of them. Baffles may merelydisrupt the pumping action of the roller cutters or they may be designed[56] References Cited to utilize the pumping action to assist intransporting UNITED STATES PATENTS cuttings toward a pickup openingthrough which the transport of the cuttings to the earths surface isinitil,686,957 lO/l928 Bull 175/313 X ated l,39l,626 9/l92l Gilthorpe...2,041,467 5/1936 Green 175/313 X 10 Claims, 4 Drawing Figures BIG HOLEDRILLING BIT BACKGROUND OF THE INVENTION The invention described hereinwas made in the course of, or under Contract AT(26-l )38 with the U. S.Atomic Energy Commission.

This invention relates to an improved rotary drill bit for boring holesin the earth. More particularly, it relates to a drill bit for drillingrelatively large diameter holes of the type wherein a plurality ofroller cutters are mounted for cutting generally in a planeperpendicular to the axis of rotation of the bit.

Recent years have seen a developing interest in the drilling ofrelatively large diameter holes up to 120- inches in diameter, and evenlarger. One type of drill bit that has been employed for drilling suchholes by rotary drilling methods utilizes a number of roller cuttersmounted on a bit plate in a manner so that, generally speaking, eachcutter engages the formation in a plane perpendicular to the axis ofrotation of the bit. Upon rotation of the bit, engagement of the teethof the roller cutters with the formation at the bottom of the holecauses rotation of the roller cutters. Successive teeth of the rollercutters engage the formation as the roller cutters rotate. Somearrangement is provided for removing the cuttings produced by the actionof the cutters on the formation from the bottom of the hole andtransporting them to the surface of the earth.

One commonly used arrangement for removing cuttings is the sweep typepickup which employs an elongated radially extending pickup opening inthe bit plate which is in fluid flow communication with one of thepassages, either cylindrical or annular, connecting the bottom of thehole with the earth's surface. These passages are formed by the drillstring, or between the drill string and the walls of the formation, orbetween two concentrically oriented drill strings if multiple stringsare employed. A circulating fluid, gas or liquid, flows across the bit,entrains cuttings therein and flows up the passage to the surfacecarrying cuttings with it. Reduced pressure on the top of the passage,injection of high pressure air into the passage, or some other means maybe used to provide the energy to lift the circulating fluid and cuttingsout of the hole through the passage to the surface of the earth. Thecriteria governing the placement of the cutters on the bit plate havegenerally been concerned with providing full coverage of the cuttingsurfaces over the entire area of the hole bottom with some redundancy.

Experience with drill bits of the type just described has not beenentirely satisfactory. Very low penetration rates have proved to be therule rather than the exception. Bit balling, bottom balling andregrinding of cuttings have been evident. Some minor improvements havebeen realized by introducing the circulating fluid to the bottom of thehole by means of jets and increasing the rate of flow across the bottomof the hole, and discarding the sweep type pickup in favor of a centerpickup. However, there are practical limits on the rate of flow ofcirculating fluid that can be achieved and analysis of the total energyexpended versus the drilling penetration rate indicated that a very lowefficiency was being obtained.

We have discovered a big hole drilling bit design with markedly improvedperformance over those used heretofore. The big hole bit according toour invention much more efficiently utilizes the total energy expendedin the drilling operation and makes it possible to obtain significantlyincreased penetration rates over previous practice.

SUMMARY OF THE INVENTION Accordingly, it is an object of this inventionto provide a big hole drilling bit that is more efficient and achievesincreased penetration rates over those used heretofore. Brieflysummarized, our drill bit takes into account the fact that individualroller cutters actually act as pumps as they rotate in conjunction withrotation of the drill bit. This pumping action of an individual rollercutter causes its own cuttings to be continuously deposited in front ofit thereby resulting in a continual regrinding of cuttings. In additionto being inefficient in itself, this contributes to bit balling andbottom balling and detracts from the desired circulation of the cuttingstoward the pickup opening. Accordingly, our drill bit incorporates meansin association with individual roller cutters which prevent the cuttingsproduced by a cutter from being deposited in front of it by the pumpingaction of the cutter. While merely blocking the flow of cuttings overthe top of the cutters provides a bit with significantly improvedperformance, we have found that designing baffle arrangements whichdirect the pumping action of individual cutters radially inwardly,generally toward the pickup opening, provides even more effectiveutilization of the total energy expended. This latter arrangementaccommodates the necessary radially inward flow of cuttings toward thepickup opening with the forced circulation of a much smaller rate offlow of circulating fluid across the bottom of the hole.

An exceedingly effective utilization of the pumping action of theindividual roller cutters is accomplished by arranging the rollercutters in a number of series wherein each successive cutter of theseries is positioned radially inward and circumferentially forward withrespect to the direction of rotation of the bit, and the baffle meansfor each cutter excepting of course the most radially inward of theseries is designed to discharge its cuttings immediately behind thesuccessive cutter, i.e., at the suction side of that roller cutter pump.The baffle means of the most radially inward cutters discharge towardthe central pickup opening. Series of roller cutters utilizing cuttershaving baffles that merely block the flow of cuttings over the cutter inaddition to cutters having baffles which discharge radially inwardlyhave also proven to be very effective under some circumstances.

A 96-inch diameter rotary drilling bit which incorporated baffle meansto control the pumping action of the roller cutters in accordance withthe foregoing accomplished penetration rates which were over severaltimes as great as those of a bit where such control was not provided.The cuttings produced by the bit using baffles contained a much smallerproportion of fine particles, indicating less regrinding of cuttings,and when the bit was extracted from the hole there was no evidence thatbottom balling or hit balling had occurred.

While the foregoing briefly summarizes an object of the invention andmeans by which it is accomplished, additional objects and details of theinvention and its numerous significant advantages will be more apparentafter consideration of the following description of preferredembodiments thereof.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective, partiallybroken away view of a drilling bit according to the invention.

FIG. 2 is a plan view of the bottom of the drill bit of FIG. 1.

FIG. 3 is a partial plan view of a drill bit incorporating anotherembodiment of th invention.

FIG. 4 is an enlarged perspective view of a roller cutter of the bit ofFIG. 3.

DESCRIPTION OF PREFERRED EMBODIMENTS Referring now to FIGS. 1 and 2,large diameter drill bit includes a bit body, or support structure, 12having a bit plate 14 and a plurality of roller cutters mounted thereon.The roller cutters include gage cutters 16, 18 and 20, interior cutters22, 24, 26, 28, and 32 and center cone cutter 34. The cutters aremounted in a conventional manner for rotation about their longitudinalaxes on saddles such as 36 and 38 in the case of gage and interiorcutters and on cantilever mount 40 in the case of center cutter 34.Conventional means are provided on the upper surface of bit body 12, notshown, for connecting bit 10 to a drill string by which the bit islowered into the hole and rotated to make hole.

Baffle arrangements 46, 48, 50, 52, 54, 56, 58, and 62 are provided, onein association with each of the gage and interior cutters. Each baffleis positioned circumferentially forward, i.e., with respect to thedirection of rotation of the bit, of the roller cutter with which it isassociated. As best shown in FIG. 1 with respect to typical bafflearrangement 54, each baffle arrangement includes an end wall 64, a sidewall 66, and a bottom baffle plate 68. Side wall 66 is formed from anangle to facilitate fastening baffle plate 68 by suitable means such asbolts 70 to the horizontally extending leg. The height of side wall 66increases with distance toward the center to give a downward slope tobaffle plate 68. Gusset 72 adds structural rigidity to the bafflearrangement.

Baffle plate 68 is preferably fabricated from a resilient material suchas rubber. Its width is selected so that there is actually a negativeclearance between forward edge 71 and the teeth of the cutter.Accordingly, successive rows of teeth of the cutter strike baffle plate68 as the cutter rotates and force the forward portion downwardly untiledge 71 slips by the row of teeth and springs upwardly toward its normalplanar relationship. This imparts a vibrating or shaking action to theplate which facilitates the flow of cuttings out of the bafflearrangement. Since the diameter of the cutter will decrease as the teethof the cutter wear down through use, the baffle plate can be made widerthan is initially necessary so that the desired negative, or at leastzero, clearance is maintained through a longer period of bit use.

As best shown in FIG. 1 in connection with baffle arrangement 48, thebaffle arrangements are open on their radially inwardly side.Accordingly, as roller 18 rotates clockwise as viewed in FIG. 1 byengagement of its teeth with the formation at the bottom of the hole androtation of bit 10 in a counter-clockwise direction as viewed in FIG. 2,cuttings and circulating fluid are pumped by the rotation of cutter 18through the space 74 between the top of the cutter and horizontalportion 76 of saddle 36. The pumping action is directed by bafflearrangement 48 through its open end 80 in a radially inward directiongenerally toward pickup opening 82 at the center of plate 14. Means notshown place pickup opening 82 into fluid flow commu- 5 nication with thesurface of the earth through one of the passages formed by the drillstring or between the drill string and the formation, or betweenmultiple drill strings if such are used, in any conventional mannerknown in the art.

As will be best seen through consideration of FIG. 2, the discharge outof the open, radially inward end 80 of baffle arrangement 48 will bringthe cuttings produced by cutter 18 to the rear of cutter 28. Since thisis the suction side of the pumping action created by the rotation ofcutter 28, cuttings produced by cutter 18, as well as the cuttingsproduced by cutter 28 itself, will be pumped over the top of cutter 28and discharged out of open, radially inward end 86 of baffle arrangement58. Those cuttings will in turn be pumped over the top of cutter 26 anddischarged out of open end 88 of baffle arrangement 56 towards pickupopening 82. It can be seen then, that the radially inward movement ofcuttings is facilitated by arranging roller cutters 18, 28 and 26 in aseries, the relative positional relationship being such that cuttingsfrom each radially outward cutter are assisted in their journey towardsthe center pickup by the pumping action of the next radially inwardcutter. It will be noted that in the drill bit depicted in FIGS. 1 and 2the three gage and six interior cutters are arranged in three suchseries of cutters. The six interior cutters are positioned on threeradii in a manner which provides redundancy of cutting surfaces over thebottom of the hole.

In the preferred embodiment of FIGS. 1 and 2 three jets, 92, 94, and 96,are positioned for discharge just behind the three gage cutters andthree jets, 98, and 102, are positioned for discharge generally in thearea of the discharge from the outlets of innermost baffle arrangements52, 56 and 60. That particular arrangement is considered to be quitesatisfactory in combination with the use of a dual string with an airlift arrangement in the inner string for providing the energy fortransporting cuttings to the earths surface. However, it is to beunderstood that the invention is not dependent upon the use of suchjets. Any arrangement which provides for movement of circulating fluidacross the bit toward the pickup should be satisfactory.

While, generally speaking, utilization of the normal pumping action ofthe roller cutters to assist in the transport of cuttings toward thepickup opening by use of baffle arrangements such as those justdiscussed in relation to FIGS. 1 and 2 is considered to be preferred,benefits can be realized by baffle arrangements which merely block thepumping action of the cutter. This will be better appreciated afterconsideration of FIGS. 3 and 4 which illustrate the manner in whichmodification of an existing big hole bit can be accomplished to gain thebenefits of the invention. As shown in FIG. 3 each of the gage cutters112, 114, 116 and 118 and interior cutters 120, 122 and 126 has inassociation therewith a baffle arrangement of the type just described inconnection with FIGS. 1 and 2. As will be apparent from examination ofFIG. 3, the existing positions of cutters 128 and 130 do not permit useof that previously described baffle arrangement. However, the blockingtype baffle arrangement of FIG. 4 can be used with cutters 128 and 130.

As shown in FIG. 4, baffle plate 132 is positioned in the space betweenthe top of roller cutter 130 and horizontal portion 134 of saddle 136.Baffle plate 132 blocks the flow of fluid and cuttings over the top ofroller cutter 130 thereby preventing the cuttings of cutter 130 frombeing deposited in front of it for regrinding. The pumping action ofcutter 130 will cause the cutting to strike baffle plate 32 resulting inturbulence behind cutter 130 which will assist in holding the cuttingsin suspension. The normal movement of the circulating fluid towardcentral pickup opening 138 will carry the suspended cuttings in thatdirection.

The blocking type baffle arrangement of FIG. 4 can also be used toadvantage with cutter 124 even though there is sufficient room for theuse of the other type of baffle arrangement. The recoil of the cuttingsoff of a blocking type baffle associated with cutter 124 would put themin closer proximity to the center of the pickup than a directed type ofbaffle previously discussed in connection with FIGS. 1 and 2. The use ofa blocking type baffle with cutter 128 would also provide someadvantages although some of the cuttings of cutter 128 will be depositedin front of cutter 130 and be reground thereby. This is considered to bepreferable to having cutter 128 regrind its own cuttings since movementtoward the center pickup is initiated. In this connection, it will berealized that advantages of the invention would be gained even if onlyblocking type baffles were utilized.

While a blocking type baffle of a particular configuration isillustrated in FIG. 4, other satisfactory arrangements will come readilyto mind. Any arrangement that blocks the flow of circulating fluid andcuttings over the top of the roller cutter will provide the desiredfunction.

While the fundamental novel features of the invention have been shownand described and pointed out as applied to embodiments particularlydescribed and further variations have been suggested and indicated byway of example, it will be readily appreciated by those skilled in theart that various omissions and substitutions and changes may be madewithin the principle and scope of the invention as expressed in theappended claims.

What we claim is:

l. A large diameter bit for producing holes in the earth by rotarydrilling comprising a cutter support structure, a plurality of rollercutters including gage cutters and a plurality of interior cuttersradially inward thereof individually mounted on the bottom of saidsupport in a manner to engage the bottom of a hole upon rotation of saidbit therein, means mounted in association with at least one of saidroller cutters for preventing cuttings produced thereby from beingdeposited in front of said cutter by the pumping action thereof, apickup opening in said support radially inward of said at least onecutter and said means mounted in association therewith and means fordirecting cuttings produced by said at least one cutter toward saidpickup opening.

2. The drill bit of claim 1 wherein said means mounted in associationwith said at least one roller cutter direct the flow of cuttingsradially inwardly.

3. The drill bit of claim 1 wherein said means mounted in associationwith said at least one roller cutter block the flow of cuttings over thetop of said cutter.

4. The drill bit of claim 1 wherein said means mounted in associationwith said at least one roller cutter are baffle arrangements provided inassociation with a plurality of individual roller cutters.

5. The drill bit of claim 4 including a series of cutters with eachsuccessive cutter being positioned radially inward and circumferentiallyforward with respect to the direction of rotation of said bit, saidassociated baffle means of at least one roller of said seriesdischarging cuttings therefrom into the region immediately behind asuccessive roller of said series.

6. The drill bit of claim 5 wherein at least one cutter of said serieshas associated baffle means which block the flow of fluid over the topof said cutter.

7. The drill bit of claim 6 wherein all of the roller cutters thereofexcept a center cutter are arranged into a plurality of said series.

8. The drill bit of claim 5 wherein each preceding roller of said serieshas associated baffle means which discharges into the region immediatelybehind its next successive roller of said series.

9. The drill bit of claim 8 wherein all of the roller cutters thereofexcept a center cutter are arranged into a plurality of said series andsaid baffle means of the innermost cutter of each series dischargetoward a pickup means adapted for connection to means for transportingcuttings out of the hole.

10. The drill bit of claim 9 wherein said pickup means is at the centerof said bit.

I "3762486 I f bct eber 2-, 197 3 Patent No I fivent o fls) WilliamGrovenburg and Robert R. Gasliff v It is cert-ifiedflthat error appearsin the above identified patent and that said Letters Patent are herebycorrected as shown below:

The middle initial "R" of lnvntof G tliff" s name should read --L-- v vY I Signed- ,and sealed this 8th giay of Oejsp-ber 1974.

(SEA

Attest: v

N c MARSHALL DANN McCOY M. GIBSQN JR. 7

Commissioner of Patents 'Att'esting Officer uscoMM-oc e037 s-pss FORMPO-1050 (10-69) I V I 4 A U.S. GOVERNMENT PRINTING OFFICE: I9590-366-334

1. A large diameter bit for producing holes in the earth by rotarydrilling comprising a cutter support structure, a plurality of rollercutters including gage cutters and a plurality of interior cuttersradially inward thereof individually mounted on the bottom of saidsupport in a manner to engage the bottom of a hole upon rotation of saidbit therein, means mounted in association with at least one of saidroller cutters for preventing cuttings produced thereby from beingdeposited in front of said cutter by the pumping action thereof, apickup opening in said support radially inward of said at least onecutter and said means mounted in association therewith and means fordirecting cuttings produced by said at least one cutter toward saidpickup opening.
 2. The drill bit of claim 1 wherein said means mountedin association with said at least one roller cutter direct the flow ofcuttings radially inwardly.
 3. The drill bit of claim 1 wherein saidmeans mounted in association with said at least one roller cutter blockthe flow of cuttings over the top of said cutter.
 4. The drill bit ofclaim 1 wherein said means mounted in association with said at least oneroller cutter are baffle arrangements provided in association with aplurality of individual roller cutters.
 5. The drill bit of claim 4including a series of cutters with each successive cutter beingpositioned radially inward and circumferentially forward with respect tothe direction of rotation of said bit, said associated baffle means ofat least one roller of said series discharging cuttings therefrom intothe region immediately behind a successive roller of said series.
 6. Thedrill bit of claim 5 wherein at least one cutter of said series hasassociated baffle means which block the flow of fluid over the top ofsaid cutter.
 7. The drill bit of claim 6 wherein all of the rollercutters thereof except a center cutter are arranged into a plurality ofsaid series.
 8. The drill bit of claim 5 wherein each preceding rollerof said series has associated baffle means which discharges into theregion immediately behind its next successive roller of said series. 9.The drill bit of claim 8 wherein all of the roller cutters thereofexcept a center cutter are arranged into a plurality of said series andsaid baffle means of the innermost cutter of each series dischargetoward a pickup means adapted for connection to means for transportingcuttings out of the hole.
 10. The drill bit of claim 9 wherein saidpickup means is at the center of said bit.